DEPT OF RADIATION ONCOLOGY

Monte Carlo dose calculations for

proton therapy on GPU

Xun Jia1, Jan Schuemann2, Drosoula Giantsoudi2, Harald Paganetti2, Steve Jiang1

1University of Texas Southwestern Medical Center 2Massachusetts General Hospital, Harvard Medical School

DEPT OF RADIATION ONCOLOGY

CAMPUS PROPER

NORTH CAMPUS

WEST CAMPUS

CLINICAL CAMPUS

SOUTH CAMPUS

PARKLAND HOSPITAL

UT Southwestern

Texas Center for Advanced

Radiation Therapy (TCART)

Current Facility

(w/ 10 Tx machines)

DEPT OF RADIATION ONCOLOGY

SCHEME A – MASSING

Phase I: Proton Center $286M, 4 gantries + 1 fixed beam Under construction

Texas Center for Advanced Radiation Therapy (TCART)

Phase II: Conventional Center $62-92M, 8+5 linac vaults Under designing

Phase III: Carbon Ion Center ~$200M Under planning

DEPT OF RADIATION ONCOLOGY

gPMC project

Monte Carlo dose calculations for proton therapy

Objective: speed up full MC dose using Graphics

Processing Units (GPU)

Develop an appropriate physics model to achieve sufficient

accuracy for proton therapy

Design GPU-friendly implementations to achieve high

computational efficiency

DEPT OF RADIATION ONCOLOGY

Proton transport Proton transport physics

Combines the physics from various literatures Kawrakow, Med Phys, 27, 485(2000), Fippel et. al., Med Phys, 31, 2263 (2004),

Penelope manual (2009), Geant4 physics manual (2011)

Energy range [0.5, 350.0] MeV

Class II condensed history simulation scheme with continuous

slowing down approximation

Multiple scattering and energy straggling

CSDA for secondary electron transport

Nuclear interaction is handled by an empirical strategy Fippel et. al., Med Phys, 31, 2263(2004)

Support 25 materials that were defined in TOPAS/Geant4

Perl et. al. Submitted to Med Phys(2012)

Voxelized patient geometry

CT to material conversion

DEPT OF RADIATION ONCOLOGY

GPU A specialized accelerator (personal super-computer)

Implementation

Nvidia CUDA environment

Optimized parallelization scheme to reduce GPU-thread divergence

Multi-dose counter to reduce memory writing conflict

Hardware supported interpolation

High-efficiency random number generator

4-16 cores >1000 cores

Jia, et. al., PMB 57, 7783 (2012)

DEPT OF RADIATION ONCOLOGY

Homogeneous phantoms Pure water

200 MeV

Other homogeneous phantoms

100, 200 MeV

Pγ = 99.9%

(2mm/2%)

Pγ > 98.7%

(2mm/2%)

DEPT OF RADIATION ONCOLOGY

Inhomogeneous phantoms

Materials

Water (0 HU)

Bone insert (500 HU)

Air insert (-1000 HU)

air

bone

water

Asquarebeam

x

z y

(a)

0 5 10 15 20 25 30

0

0.2

0.4

0.6

0.8

1

1.2

0 4 8 12

z (cm)

0.1

0.6

1.1

D (MeV/g)

TOPAS/Geant4, bonegPMC, boneTOPAS/Geant4, airgPMC, air

(b) (c)

bone air

0 5 10 15 20 25 30

0

0.2

0.4

0.6

0.8

1

1.2(b)

-4 -2 0 2 4

x (cm)

0.1

0.6

1.1

D (MeV/g)

TOPAS/Geant4, 6cmTOPAS/Geant4, 12cmgPMC, 6cmgPMC, 12cm

(c)

bone air

lung

bone

water

Asquarebeam

x

z y

(a)

0 5 10 15 20 25 30

0

0.2

0.4

0.6

0.8

1

1.2

0 4 8 12

z (cm)

0

1

2

D (MeV/g)

TOPAS/Geant4, boneTOPAS/Geant4, lunggPMC, bonegDPM, lung

(b)

-4 -2 0 2 4

x (cm)

0

1

2

D (MeV/g)

TOPAS/Geant4, 6.95cmTOPAS/Geant4, 10.85cmgPMC, 6.95cmgPMC, 10.85cm

(c)

bone lung

0 5 10 15 20 25 30

0

0.2

0.4

0.6

0.8

1

1.2

0 4 8 12

z (cm)

0

1

2

D (MeV/g)

TOPAS/Geant4, boneTOPAS/Geant4, lunggPMC, bonegDPM, lung

(b)

-4 -2 0 2 4

x (cm)

0

1

2

D (MeV/g)

TOPAS/Geant4, 6.95cmTOPAS/Geant4, 10.85cmgPMC, 6.95cmgPMC, 10.85cm

(c)

bone lung

Pγ = 99.9%

(2mm/2%)

DEPT OF RADIATION ONCOLOGY

Patient case

gPMC TOPAS/GEANT4

γ-index distribution

(2%/2mm)

CTV: Pγ = 99.75%

GTV: Pγ = 99.90%

Whole patient:

Pγ = 99.94%

DEPT OF RADIATION ONCOLOGY

Efficiency

GPU: NVIDIA Tesla C2050

CPU computation time is 2~80 CPU hrs

Phantom Source

Energy (MeV)

<σ/D>

(%)

T

(sec)

Water 100 0.9 6.76

200 1.1 21.14

Bone 100 0.9 6.68

200 1.1 20.98

Tissue 100 0.9 7.08

200 1.1 22.29

Inhomogeneous phantom 100 0.9 9.44

Patient # Beam # Npart

(M)

Tload

(sec)

Tsim

(sec)

Pγ

(%)

1

1 10.8 15.5 16.2 97.5

2 10.7 15.2 13.3 98.0

3 7.6 11.2 10.8 97.4

4 8.4 12.5 12.6 97.7

5 5.6 9.2 8.6 97.4

2

1 6.8 10.6 5.5 99.2

2 7.1 10.5 5.7 99.4

3 7.3 10.7 5.8 99.6

DEPT OF RADIATION ONCOLOGY

Real-time Reconstruction of The Delivered Dose

DEPT OF RADIATION ONCOLOGY

Summary

gPMC: GPU-based MC dose calculation package for proton

therapy

The accuracy is validated against TOPAS/Geant4

Dose calculation time is 6~22 sec

http://www.forbes.com/sites/netapp/2014/06/02/video

-game-cure-cancer/

This work was featured by Forbes Magazine

on June 2nd, 2014

Steve.Jiang@UTSouthwestern.edu

The 5th Short Course in GPU Programming on 9/3-4

The code can be shared for research purpose